Method for preparing adsorptive cellulose ethers

ABSTRACT

ADSORPTIVE CATIONIC CELLULOSE IS PREPARED BY INTRODUCING CATIONIC SUBSTITUENTS ONTO CELLULOSE IN AN ALKALINE AQUEOUS SOLUTION OF A SALT OF A STRONG ACID AND A STRONG BASE. THE DERIVATIZED CELLULOSE HAS A HIGH ADSORPTIVE CAPACITY FOR CERTAIN PROTEINACEOUS MATERIALS, E.G., ENZYMES.

United States Patent 3,823,133 METHOD FOR PREPARING ADSORPTIVE CELLULOSEETHERS Louis S. Hurst and Norman E. Lloyd, Clinton, Iowa, assignors toStandard Brands Incorporated, New York, No Drawing. Continuation-impartof abandoned application Ser. No. 254,513, May 18, 1972. Thisapplication May 17, 1973, Ser. No. 361,361

Int. Cl. C08b 11/00 US. Cl. 260-231 A 11 Claims ABSTRACT OF THEDISCLOSURE Adsorptive cationic cellulose is prepared by introducingcationic substituents onto cellulose in an alkaline aqueous solution ofa salt of a strong acid and a strong base. The derivatized cellulose hasa high adsorptive capacity for certain proteinaceous materials, e.g.,enzymes.

THE INVENTION This application is a continuation-in-part of applicationSer. No. 254,513 filed May 18, 1972, now abandoned.

This invention relates to a process for preparing adsorptive celluloseethers. More particularly, the invention relates to a process forpreparing adsorptive cellulose ethers having cationic substituents.

Cellulose can be derivatized to form insoluble materials having theadvantages of rigidity, inertness, large surface area, and, due to itsopen, porous structure, high adsorptive capacity.

Cellulose occurs in the form of anhydroglucose units bound together byglucosidic linkages. Each anhydroglucose unit has at least three freehydroxyl groups capable of undergoing substitution reactions to formethers, esters, etc. The average number of hydroxyl groups substitutedper anhydroglucose unit of cellulose is known as the degree ofsubstitution (D.S.). It is theoretically possible to obtain cellulosederivatives having a BS. of 3. Effective adsorbents can be produced,however, having a D8. substantially lower than this value. Withincreasing D.S., cellulose derivatized with polar substituents, for themost part, tends to become increasingly water soluble.

Dialkylaminoalkyl derivatives are conventionally pre* pared in areaction mixture containing limited amounts of Water in order to reducethe extensive degree of hydrolysis that aminoalkylating agents undergoin aqueous systems. Thus, in the preparation of cationic celluloses byetherifi cation low water to cellulose ratios are used in the reactionmixtures, for instance, about six parts of water to one part cellulose.Because of the low proportion of water present, the mixture is aplastic-like mass and requires extensive mixing to obtain intimatecontact between the reactants. Relatively large energy expenditures arerequired to effect this mixing. Larger quantities of water in proportionto the amount of cellulose greatly reduced the reaction efficiency dueto hydrolysis of the derivatizing agent with the result that largeamounts of the agents are required to achieve the desired degree ofsubstitution. Organic solvents have frequently been used as suspensionmedia for mixing the reactants, but they present certain safety hazardsand are costly to use and recover.

There are a number of patents and publications relating to thepreparation of derivatized cellulose. US. Pat. 3,357,971 to Klugdiscloses the preparation of mixed ethers of cellulose having a cationicD.S. of from 0.001 to 0.4 and a non-ionic MS. of 2 (MS. is the averagenumber of moles of reactant reacted with cellulose per anhydroglucoseunit). These products are water soluble which prohibits their use asadsorbent materials. US. Pat. 3,095,410 to Anslow discloses thepreparation of a diethylaminoethyl (DEAE) cellulose having an ion-ex-Patented July 9, 1974 ice change capacity of 0.3 to 1.5 milliequivalentsper gram. Both of the aforementioned references disclose having presentin the reaction mixture low water to cellulose ratios. Publications byPetersen and Sober, J.A.C.S., 78, 751 (1956) and by Guthrie and Bullock,I EC, 52, 935 (1960) also describe methods for preparing adsorptivecellulose products in reaction mixtures having low water to celluloseratios.

It is an object of the present invention to prepare adsorptive cationiccellulose by a slurry process whereby the cellulose is derivatized byetherification in a reaction mixture having a relatively high water tocellulose ratio.

It is another object of the present invention to prepare adsorptivecationic cellulose by a slurry process whereby cellulose is derivatizedby etherification in a reaction mixture having a relatively high waterto cellulose ratio under conditions which result in improved reactionefiiciency.

It is still another object of the present invention to provide a processfor preparing adsorptive cationic cellulose whereby relatively smallamounts of derivatizing agents are required to attain the desired degreeof substitution.

These objects and other objects of the present invention which will beapparent from the following description are attained in accordance withthe present invention by reacting cellulose with a cationic etherifyingagent in an alkaline aqueous solution of a salt of a strong acid and astrong base.

Cationic etherifying agents used in the present process may berepresented by the following general formula:

where: R, and R are selected from the group consisting of hydrogen,alkyl, hydroxyalkyl, alkenyl or aryl radicals containing up to 7 carbonatoms; R, is an alkyl, hydroxyalkyl or alkenyl radical containing up to6 carbon atoms; R, is an alkyl or an alkenyl radical having up to 7carbon atoms, or an alkyl or an alkenyl radical having up to 7 carbonatoms substituted with a chloro, bromo, iodo, or epoxy group; R and Rmay be joined to form a nitrogencontaining heterocyclic ring containingup to 6 carbon atoms; X is an anion; R and X may be absent in which casethe cationic etherifying agent is an uncharged free amine.

Illustrative of examples of compounds of the above type are:Z-dimethylaminoethyl chloride hydrcohloride, 2- diethylaminoethylchloride, 2 dimethylaminoisopropyl bromide hydrochloride,2-dia1lylaminoethyl chloride, 3-dimethylaminopropyl bromide, 2diisopropylaminoethyl chloride hydrochloride, N-(2,3-epoxypropyl)dimethylamine, N-(2,3-epoxypropyl) dibutylamine hydrochloride,N-(2,3-epoxypropyl) piperidine hydrobromide, N-(2,3 epoxypropyl)phenyldimethylammonium chloride, N-(2, 3 epoxypropyl) trimethylammoniumchloride, N-(2,3- epoxypropyl) triethylammonium bromide, and N,Ndiethylaziridinium chloride.

The preferred etherifying agent is diethylaminoethyl chloride or itshydrochloride.

While a number of cellulosic materials are suitable for etherificationby the process of the present invention, it is preferred that thecellulosic material have an alpha cellulose content of at least aboutpercent. There are a number of cellulose products available havingvarying degrees of porosity as measured by the procedure set forthhereinafter. The initial porosity or porosity of the cellulose prior toderivatization has a significant effect on the degree of DEAEsubstitution and on the resulting adsorption capacity of the derivatizedcellulose. In general, the lower the porosity of the cellulose, thegreater its surface area and reactivity, and consequently, the greaterthe degree of DEAE substitution which can be obtained with a givenamount of derivatizing agent and the higher the adsorption capacity ofthe derivatized cellulose. It is a preferred embodiment of the presentinvention that the initial prosity of the cellulose be below about 1 andit is a most preferred embodiment that the initial porosity be in therange of from about 0.2 to about 0.05 ml. cm. mingf. If the initialporosity of the cellulose is very low, the porosity of the DEAEcellulose may be too low to permit easy filtration.

The etherification reaction may be carried out by preparing an alkalineaqueous slurry of cellulosic material having present a salt of a strongbase and a strong acid and an etherifying agent of the type describedabove and maintaining the slurry under suitable reaction conditions.

Generally, the amount of alkali present in the slurry is suflicient toprovide from about 0.4 to about 6 moles f alkali per mole of alphacellulose in the cellulosic material. The molecular weight of alphacellulose is assigned a value of 162. Preferably, the amount of alkalipresent in the slurry is sufficient to provide from about 2 to about 4moles of alkali per mole of alpha cellulose in the cellulosic materialand most preferably from about 2.5 to about 3.5 moles of alkali per moleof alpha cellulose.

The proportion of water to cellulosic material in the slurry should besuch as to provide a water to cellulose ratio of from about 6:1 to about25:1 on a weight basis. The preferred ratio is from about 8:1 to about20:1 and the most preferred ratio is from about 10:1 to about 14:1 onthe same weight basis.

The D.S. obtained will be dependent upon the reaction temperature, thereacting period and the amount of cationic etherifying agent used. Ingeneral, the longer the etherification reaction is allowed to proceed,the higher will be the D5. until the etherifying agent is completelyconsumed.

As noted above, the D.S. of the cellulose should be sufiicient toprovide an effective cationic adsorbent but insufficient to result inthe production of a soluble product. Effective DEA-E (diethylaminoethyl)cellulose adsorbents prepared by the present process will typically havean amine D8. of from about 0.05 to about 0.4. The preferred amine D.S.is from about 0.07 to about 0.3 and the most preferred amine D.S. isfrom about 0.1 to 0.2. The amount of cationic etherifying agent added tothe cellulose slurry to provide the desired range of amine D5. willtypically be from about 0.2 to about 1.5 moles of etherifying agent permole of alpha cellulose. The most preferred amount is from about 0.6 toabout 0.8 moles of cationic etherifying agent per mole of alphacellulose.

The concentration of the salt of a strong acid and strong base in theslurry will typically be in the range of from about 0.3 to about 5 molarand preferably from about 1 to about 4 molar. The most preferred saltconcentration is from about 2.5 to about 3.5 molar.

The preferred salt of a strong base and strong acid used in the presentprocess is sodium sulfate. The presence of salts of this type in thereaction mixture surprisingly reduces the deleterious effects of waterand permits the reaction to be performed at high water to celluloseratios while maintaining a reaction efficiency comparable to thatobtained when lower water to cellulose ratios are used. While thepresent invention is not limited to any theory, it is thought that thesalt of a strong base and a strong acid ties up some of the waterpresent in the slurry, thus reducing hydrolysis of the etherifyingagents. A higher water to cellulose ratio results in a more uniformsubstitution on the cellulose because of the ease with which the slurrymay be mixed. Organic solvents have been used to make cellulose ethersbut this is not desirable because of the hazards involved and theeconomies.

In a preferred embodiment of the present invention, non-ionicsubstituents as well as cationic substituents are introduced onto thecellulose to provide a mixed ether derivative of cellulose. Illustrativeof examples of agents for introducing non-ionic substituents arealkylene oxides,

e.g., ethylene, propylene or butylene oxides and alkyl halides, e.g.,methyl, propyl, benzyl, and allyl chlorides, bromides and iodides.Acrylonitrile may also be used to introduce non-ionic substituents ontothe cellulose. The preferred non-ionic agent is ethylene oxide.

The adsorptive mixed cellulose ethers of the present invention willtypically have a non-ionic MS. of from about 0.01 to about 0.5 andpreferably of from about 0.08 to about 0.3, the cationic D.S. being asindicated above. To achieve the desired degree of non-ionic substitutionin the mixed ether derivative, the amount of non-ionic etherifying agentadded will usually be from about 0.02 to about 0.5 moles of non-ionicagent per mole of alpha cellulose and preferably from about 0.1 to about0.4 moles of nonionic agent per mole of alpha cellulose.

Generally, it is preferred to react the celulose with the non-ionicagent prior to carrying out the reaction with the cationic etherifyingagent. For this purpose, the nonionic agent and the cationic etherifyingagent may be dissolved and added separately to the celulose slurry withstirring, the solution containing the non-ionic etherifying agent beingadded first. The etherification reaction may be carried out over arelatively wide temperature range but the preferred temperature range isfrom about 30 to about C.

The introduction of non-ionic groups onto celulose in addition to thepresence of cationic substituents results in the formation of a mixedether derivative of cellulose with increased adsorptive capacity. It isbelieved that the non-ionic groups have the effect of increasing theavailable surface area of the cellulose and thereby increasing theavailability of the cationic groups.

Since non-ionic derivatizing agents are less expensive than cationicagents, the process of the present invention also provides a moreeconomical method of preparing adsorptive cationic cellulose.

The cationic celulose ethers of the present invention have a highadsorptive capicity for certain proteinaceous materials, such asenzymes. In industrial applications, enzymes are conventionally used insoluble form, which practice largely precludes their continuous use.While it is theoretically possible and economically desirable to recoverand reuse soluble enzymes, the economics of so doing has generally madethis impractical. When the adsorptive cellulose of the present inventionis contacted by an aqueous solution containing an enzyme, e.g., glucoseisomerase, the enzyme is adsorbed onto the cellulose and is therebyinsolubilized or immobilized.

In order to more clearly describe the nature of the present invention,specific examples will hereinafter be described. It should beunderstood, however, that this is done solely by way of example and isintended neither to delineate the scope of the invention nor limit theambit of the appended claims. In the examples and throughout thisspecification, percentages are utilized to refer to percent by weightunless otherwise stated.

IGIU

IGIU is the abbreviation for International Glucose Isomerase Unit and isthat amount of enzyme which will convert 1 micromole of glucose tofructose per minute in a solution initially containing 2 moles ofglucose per liter, 0.02 moles of MgSO per liter and 0.001 mole of CoClper liter at a pH of 6.84 to 6.85 (0.2M sodium maleate) and atemperature of 60 C. Glucose isomerase determinations were carried outby the method of N. E. Lloyd et al., Cereal Chem., 49, No. 5, pp.544-553 (1972).

ADSORPTION CAPACITY Determined by a continuous method in which anaqueous glucose isomerase preparation derived from Streptomyces sp. ATCC21175, containing about 10 IGIU/ml. is metered at 1.5 mL/min. into aslurry containing 0.5 gram of the cationic celulose ether in ml. ofwater at pH 7.0. Simultaneously, a small portion of the aqueous phase ofthe slurry is continuously removed at 0.4 ml./ min. through a filterprobe and analyzed continuously for glucose isomerase by the above notedmethod. As the glucose isomerase preparation is added, the isomerase iscontinuously adsorbed on the cationic cellulose ether. No appreciableisomerase activity appears in the liquid phase of the slurry untilenough isomerase has been added to exceed the adsorption capacity of thecationic cellulose ether. A plot of the glucose isomerase concentrationin the aqueous phase of the slurry versus the total amount of isomeraseadded to the slurry is made and a straight line drawn through the linearportion of the curve is extrapolated to zero concentration of glucoseisomerase. The total IGIU adsorbed, at this point, per gram of cationiccellulose ether is the adsorption capacity of the cationic celluloseether.

INITML POROSITY Fifteen grams of dry cellulose powder is slurried inwater and the slurry deaerated by stirring under vacuum for minutes. Aglass column (1.5 inches inside diameter, 18 inches high) fitted with aporous glass disc and a stopcock at the bottom is attached to a vacuumflask through a rubber stopper. The flask is in turn attached to avacuum source. The deaerated slurry of celulose powder is poured intothe column and a vacuum (12.3 p.s.i. below atmospheric pressure) isapplied to the bottom of the column by opening the stopcock. Thecellulose powder is collected on the porous glass disc to form a packedbed. Simultaneously, water is admitted at the top of the column toreplace that removed by filtration so that about 5 inches of water ismaintained above the packed bed at all times. When a total of 1,000 ml.of water has been collected, the stopcock is closed, the flask removedand the water emptied from the flask. The flask is then reattached tothe column, the vacuum reestablished, the stopcock opened and a measuredquantity (1,000 to 3,000 ml.) of water is filtered through the packedcellulose bed and collected. The time required to collect the water isdetermined with a stop watch. The porosity constant is calculated usingthe following equation:

K=(VH)/(TPA) Where:

K porosity constant (ml. cm. g minr V=volume of water collected (ml.)

H=height of packed bed (cm.)

T=time to collect the water (min.) P=pressure drop across bed (g persquare cm.) A=cross section of bed (square cm.)

EXAMPLE I This Example illustrates the effect of reacting a cationicetherifying agent with cellulose in an alkaline aqueous solution ofsodium sulfate.

64 grams of sodium hydroxide was dissolved in 1620 ml. of water, in thesame volume of a 10 percent sodium sulfate solution and in the samevolume of a 20 percent sodium sulfate solution. 162 grams of cellulose(BW- Solka Floc manufactured by Brown Co., Berlin, N.H.) was blendedinto each solution and 94.5 grams of diethylaminoethyl chloridehydrochloride, hereinafter referred to as DEC, was slowly sifted intoeach slurry with stirring. The slurries were heated at 80 C. for aperiod of 30 minutes with continuous stirring. The slurries ofdiethylaminoethyl cellulose were cooled, adjusted to a pH of 4 by theaddition of a dilute solution of hydrochloric acid, filtered and thefilter cakes washed with water. The filter cakes were slurried in water,filtered, and the filter cakes again washed with water. The cake weredried at a temperature of 170 F. to a moisture content of about 5percent.

Moles of DEAE substitution per mole of reactant (DEG) X100.

From the above table it is seen that as the amount of sodium sulfate inthe reaction mixture was increased, there was an increase in both theD.S. of the DEAE cellulose and the reaction efficiency.

EXAMPLE II This Example demonstrates the effect of introducing non-ionicand cationic substituents onto cellulose on the adsorption capacity ofthe cellulose.

3.5 grams of ethylene oxide was incorporated at ambient temperature intoan aqueous slurry containing 54 grams of cellulose (C-l00, manufacturedby International Filler Corporation, North Tonawanda, N.Y.), 650 gramsof water, 390 grams of sodium sulfate and 16 grams of sodium hydroxide.The temperature of the slurry was then increased to 45 C. over a periodof 20 minutes and then 25 grams of DEC was added. After stirring for 75minutes at 45 C., the slurry was cooled, adjusted to a pH of 4 by theaddition of the dilute solution of hydrochloric acid, filtered andwashed in the manner described in Example I.

Another cationic cellulose was prepared in the manner described above,except that no ethylene oxide was used.

The properties and the adsorption capacity of the celluloses are setforth in Table II below.

Based on percent of added ethylene oxide reacting with the cellulose toform hydroxyethyl groups.

From the above table it is seen that the introduction of non-ionicgroups onto the cationic cellulose increased the adsorption capacity ofthe cellulose.

EXAMPLE III This Example illustrates the effect of varying the type ofcellulose, reactant ratios, reaction periods and reaction temperatureson the adsorption capacity of the cationic cellulose obtained.

The amounts of the constituents used in the reactions and the conditionsunder which the reactions were carried out are set forth in Table III,and the results are set forth in Table IV. For the preparation of eachsample, a mixture of two different celluloses with a total weight of 50grams was etherificd. Cellulose C-l00 was a knife ground softwoodcellulose and cellulose BW-40 was a ball milled hardwood cellulose. Thecellulose mixture was added to a solution containing the indicatedamounts of water, sodium sulfate, and sodium hydroxide (see columnheaded NaOH The ethylene oxide was added and etherification conducted bystirring the mixture for the time and at the temperature indicated (seeunder Ethylene Oxide Reaction Conditions). At the end of theetherification step with ethylene oxide, additional sodium hydroxide(see under column headed NaOH was added to the reaction mixture, thereaction mixture adjusted to the indicated temperature, the DEC added,and the mix ture then stirred for the time indicated (see under DECReaction Conditions). After etherification with the DEC, the resultingreaction mixture was neutralized, washed, and dried in the mannerdescribed in Example I.

TABLE 111 Grams of constituent used Ethylene oxide reaction DEC reactionCellulose conditions conditions Ethylene Temp. Time Temp. Time SampleNo. C-lOO e BW-40 b oxide EC H NazSOl NaOH NaOH 0.) (hrs.) 0.) (hrs.)

e Alpha cellulose floc, C-100, International Filler Corp. b Solka-Floc,BW-40, Brown Company. B Used in ethylene oxide reaction. 6 Used in DECreaction.

TABLE 1V.R E S U L T S OF EXPERIMENTS SHOWN IN TABLE V TABLE III InitialAdsorpt on 30 porosity, Adsorption Non-ionic capacity Cellulose ml. cm.g.- DEAE capacity, Amine D.S. M.S. of DEAE (IGIU, g source min- DS.IGIU/g.

of DEA cellulose of DEAE cellulose (calculated) cellulose) (1) BW-40 O.10 0.14 2, 3 24 (2) SW-40- 0. 16 0. 12 1, 330 0. 09 0. 16 1, 300 (3)-C100 0. 60 0. 13 1, 770 0. 14 0. 08 2, 460 (4) RB-IOO- 0. 80 0. 10 1,050 0. 11 0. 16 1, 900 (5) BH-- 0. 07 0. 14 2, 240 0. 16 0. 16 2, 800(6) Cotton80* 0. 10 0. 13 2, 100 0. 10 0.16 1, 360 0. 11 0. 08 1, 230Ground to pass through an 80 mesh U.S. Standard screen. 0. 12 0. 08 2,430 Identification of celluloses: 0. 15 0.08 1, 900 (1) and (2), BrownCompany. 0. 11 0. 16 2,400 (3) (4) and (5), International Filler Corp.0.12 0. 08 1,450 40 (0) ER 1600, Buckeye Cellulose Corp. 0. 15 0. 16 2,540 o. 09 0. 03 1,220 From the results shown In the above table it isapg- 3 8- g g 223 parent that, in general, the celluloses having lowerlmtlal 0.14 0.17 2,700 porosity had greater degrees of DEAE substitutionand 8-13 3' 13 338 higher adsorption capacities for glucose isomerase.0.16 0.22 3, 030 The terms and expressions which have been employed 8-8' g? 2 $28 are used as terms of description and not of limitation, o.17 0. 26 3, 420 and it is not intended, in the use of such terms and ex-0 17 0. 28 2, 970

Based on 80 percent of the added ethylene oxide reacting with thecellulose to form hydroxyethyl groups.

EXAMPLE IV This Example illustrates the effect of initial porosity ofvarious celluloses obtained from a number of sources on the degree ofDEAE substitution and adsorption capacity for glucose isomerase of thederivatized cellulose.

Six samples of cellulose having varying initial porosities werederivatized in the following manner: 23 grams of sodium hydroxide wasdissolved in 440 ml. of a 20 percent sodium sulfate solution. 54 gramsof dry substance cellulose was blended into the alkali salt solutionwith vigorous stirring. 34.4 grams of DEC dissolved in 100 ml. of a 20percent sodium sulfate solution was added slowly to the alkali celluloseslurry with stirring. The cellulose-DEC slurry was then heated at 60 C.for one hour with continuous stirring. The reaction mixture wasneutralized to pH 4 with dilute HCl and filtered and the derivatizcdcellulose on the filter was washed with water. The filter cake wasreslurricd in fresh water, and the slurry filtered. The derivatizedcellulose was then rinsed with water and dried at 170 F. to a moisturecontent of about 5 percent.

The initial porosity, degree of DEAE substitution and adsorptioncapacity for glucose isomerase obtained for the various celluloses areshown in Table V.

pressions, to exclude any equivalents of the features shown anddescribed or portions thereof, since it is recognized that variousmodifications are possible within the scope of the invention claimed.

What is claimed is:

1. A method for preparing adsorptive cationic cellulose comprisingreacting cellulose with a cationic etherifying agent in an alkalineaqueous solution containing an amount of a salt of a strong acid and astrong base sufficieut to increase the reaction efliciency between thecationic etherifying agent and the cellulose, wherein the cationicetherifying agent is represented by the following general formula:

where: R and R are selected from the group consisting of hydrogen,alkyl, hydroxyalkyl and alkenyl or aryl radicals containing up to 7carbon atoms; R is an alkyl, hydroxyalkyl or alkenyl radical containingup to 6 carbon atoms; R; is an alkyl or an alkenyl radical having up to7 carbon atoms, or an alkyl or alkenyl radical having up to 7 carbonatoms substituted with a chloro, brorno, iodo, or epoxy group; R and Rmay be joined to form a nitrogen-containing heterocyclic ring containingup to 6 carbon atoms; X is an anion; R and X may be absent in which casethe cationic etherifying agent is an uncharged free amine.

2. A method for preparing adsorptive cationic cellulose as defined inClaim 1, wherein, the etherifying agent is diethylaminoethyl chloride orthe hydrochloride thereof.

3. A method for preparing adsorptive cationic cellulose as defined inClaim 2, wherein the salt of a strong acid and a strong base is sodiumsulfate.

4. A method for preparing adsorptive cationic cellulose as defined inClaim 1, wherein the cellulose is also reacted with an agent capable ofintroducing non-ionic substitutents onto the cellulose.

5. A method for preparing adsorptive cationic cellulose as defined inClaim 4, wherein the agent capable of introducing non-ionic substituentson the cellulose is ethylene oxide.

6. A method for preparing adsorptive cationic cellulose as defined inClaim 4, wherein the cellulose is reacted with diethylaminoethylchloride or the hydrochloride thereof under conditions such that thecationic cellulose as a BS. of from about 0.05 to about 0.4.

7. A method for preparing adsorptive cationic cellulose as defined inClaim 4, wherein the cellulose is reacted with diethylaminoethylchloride or the hydrochloride thereof under conditions such that thecationic cellulose has a D8. of from about 0.07 to about 0.30.

8. A method for preparing adsorptive cationic cellulose as defined inClaim 1, wherein the cellulose is reacted with an agent capable ofintroducing non-ionic substituents onto the cellulose under conditionssuch that the resulting cationic cellulose has a non-ionic MS. of fromabout 0.01 to about 0.5.

9. A method for preparing adsorptive cationic cellulose as defined inClaim 8, wherein the cellulose is reacted with an agent capable ofintroducing non-ionic substituents onto the cellulose under conditionssuch that the resulting cationic cellulose has a non-ionic M.S. of fromabout 0.08 to about 0.3.

10. A method for preparing adsorptive cationic cellulose as defined inClaim 9, wherein the cellulose has an initial porosity, of below about 1ml. cm. 6- min.

11. A method for preparing adsorptive cationic cellulose as defined inClaim 10, wherein the cellulose has an initial porosity, of from about0.2 to about 0.05 ml. cm. 6- min- References Cited UNITED STATES PATENTS1,863,208 6/1932 Schorger 260-231 A 3,095,410 6/1963 Anslow 260-231 A3,337,531 8/1967 Wakeman et al 260-215 3,357,971 12/1967 Klug 260-2153,359,258 12/1967 Toms 260-231 A 3,494,719 2/ 1970 Soignet et al 260-231A 3,526,475 9/1970 Soignet et a1. 260- 3,676,423 7/1972 Elizer 260-215MAURICE J. WELSH, Primary Examiner R. W. GRIFFIN, Assistant Examiner US.Cl. X.R. 8-120; 260-215 UNI 'IED'STATES PATENT OFFER; CERTIFICATE 0FCORRECTION I} Patent No. 3,823,133 r Dated July 9,197

Inventofls) Louis" S. Hurst and Norman E. LloVd I It; is cerfi fiiedNth'at error appears in the above-identified patent and that saidLetters Patent are hereby corrected as shown below:

Column 1, 1 1,657; "reduced" should read 'r d ce--.'

' column 2, 1156 A8; 1"z-dim ethylamino-eflgofifdfifi hygmgohlridew k-2-dimethylamirioethyl I id?-.* Yd 9h;

i 1'6; '20)" 26, 37 and 74 "cel ilose" should read; -oellulos'e. i I 1we: v Column 5; lipefg25 g 'cel ulose' shoul d read fQEillllOSQ-vQ Icolumn 6; li e-28; "the dilute solution shou d read --a dilutesvolution--.. Column '8, Teble V, 1ine fl3l5 delete comma after "g 1CQlumri -BQ-IableV, l'in'e 32; "us." should rea 1-:--'D.s.--

Column 9.; li g 12; "substitutents should read- --substitue'nts' 1 Y ,1Column 9, line 21; "as" should read --ha.s C'oliimn lO lin'e 9-;betwe'en o s ar 1 f delete v comma "G min." Should read gv min oolumnlo;line 12; between "porosity" and. "of" delete comma. A r '7 1 column 10,like 13; "o' shoul ead f (SEAL) Attest: l I I McCOY M. .GIBSONJR; o.MARSHALL DANN N Attesting Offioer I I comis'sionz ofi Patents FORM Poosou'o-es) v v e f. USCOMWDC V GOVERNMENT PRINTING OIFFICE: I," 35"I3l

